The pathway of AMP catabolism in several prokaryotes involves AMP nucleosidase. In Azotobacter vinelandii, this enzyme is responsible for regulation of AMP levels. The metabolic significance of such regulation is not well documented. Experiments are planned to measure the changes in adenine nucleotide levels in cells which are deficient in AMP nucleosidase. Current studies have demonstrated that mutants with only a few percent of the wild type AMP nucleosidase levels are still capable of regulating intracellular AMP levels. Mutants which are free of the nucleosidase will be selected and the adenylate levels studied under varying metabolic conditions.